The Commute Atlanta program is an instrumented vehicle research program funded by the FHWA Value Pricing Program and the Georgia Department of Transportation. A major objective for the multiyear program is to assess the effects of converting fixed automotive costs into variable driving costs. The main research hypothesis is that given a per mile pricing system, participants will modify their driving patterns in an effort to reduce their total costs, pocketing the savings. The Commute Atlanta project includes the parallel collection of instrumented vehicle data, household sociodemographic surveys, 2-day travel diaries, and employer commute options surveys. The research team will monitor the changes in driving patterns and will use statistical analyses of household characteristics, vehicle travel, and relevant employer survey data to examine the relationships between the incentives offered and subsequent travel behavior changes. This paper focuses on the recruitment methods and travel diary response rates for the 2-day diary surveys conducted in February and March 2004. As in other instrumented vehicle studies, researchers collected data that allow the comparison of reported diary travel with monitored vehicle travel. However, this paper focuses on a new type of comparison. Because the households had been recruited into the study 8 months before the diary study and their vehicles were transmitting activity data, the research team could examine whether there were differences in household vehicle activity between that 77% of households that completed the diary data collection and the 23% that did not. The differences were significant at both the high and low ends of the travel-reporting spectrum and may have some major implications for evolving household travel survey methods.
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